import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.concurrent.*;

/**
 * Created by ScorpionOrange on 2016/11/13.
 */
public class ThreadPoolTest {
    public static void main(String[] args) throws Exception{
        Scanner in = new Scanner(System.in);
        System.out.print("Enter base directory (e.g. /usr/local/jdk5.0/src):");
        String directory = in.nextLine();
        System.out.print("Enter keyword (e.g. volatile):");
        String keyword = in.nextLine();

        ExecutorService pool = Executors.newCachedThreadPool();

        MatchCounter counter = new MatchCounter(new File(directory), keyword, pool);
        Future<Integer> result = pool.submit(counter);

        try{
            System.out.println(result.get() + " matching files.");
        }
        catch (ExecutionException e){
            e.printStackTrace();
        }
        catch (InterruptedException e){}

        pool.shutdown();

        int largesPoolSize = ((ThreadPoolExecutor) pool).getLargestPoolSize();
        System.out.println("largest pool size = " + largesPoolSize);
    }
}

/**
 * This task counts the files in a directory and its subdirectories that contain a given keyword.
 */
class MatchCounter implements Callable<Integer>{
    private File directory;
    private String keyword;
    private ExecutorService pool;
    private int count;

    /**
     * Constructs a MatchCounter.
     * @param directory the directory in which to start the search
     * @param keyword the keyword to look for
     * @param pool the thread pool for submitting subtasks
     */
    public MatchCounter(File directory, String keyword, ExecutorService pool){
        this.directory = directory;
        this.keyword = keyword;
        this.pool = pool;
    }

    public Integer call(){
        count = 0;
        try{
            File[] files = directory.listFiles();
            List<Future<Integer>> results = new ArrayList<>();

            for(File file : files){
                if(file.isDirectory()){
                    MatchCounter counter = new MatchCounter(file, keyword, pool);
                    Future<Integer> result = pool.submit(counter);
                    results.add(result);
                }
                else {
                    if(search(file)) count++;
                }
            }
            for(Future<Integer> result : results){
                try{
                    count += result.get();
                }
                catch (ExecutionException e){
                    e.printStackTrace();
                }
            }
        }
        catch (InterruptedException e){}
        return count;
    }

    /**
     * Searches a file for a given keyword
     * @param file the file to search
     * @return true if the keyword is contained in the file
     */
    public boolean search(File file){
        try{
            try(Scanner in = new Scanner(file)){
                boolean found = false;
                while (!found && in.hasNextLine()){
                    String line = in.nextLine();
                    if(line.contains(keyword)) found = true;
                }
                return found;
            }
        }
        catch (IOException e){
            return false;
        }
    }
}
